Sally Furniss
Well-known member
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Chikungunya virus
CHIK is responsible for extensive Aedes aegypti-transmitted urban disease in cities in Africa and major epidemics in Asia. The crippling arthralgia and frequent arthritis that accompany the fever and other systemic symptoms are clinically distinct. Several other togaviruses of the alphavirus genus (Ross River, O?nyong-nyong, etc) have been associated with a similar syndrome. CHIK activity in Asia has been documented since its isolation in Bangkok in 1958. Other countries which have reported CHIK activity include Cambodia, Vietnam, Myanmar, Sri Lanka, India, Indonesia, and the Philippines.
CHIK virus is transmitted in the savannahs and forests of tropical Africa by Aedes mosquitoes of the subgenera Stegomyia and Diceromyia. Aedes aegypti is an important vector in urban epidemics in both Africa and Asia.
Clinical Features
CHIK is an acute infection of abrupt onset, heralded by fever and severe arthralgia, followed by other constitutional symptoms and rash, and lasting for a period of 1-7 days. The incubation period is usually 2-3 days, with a range of 1-12 days. Fever rises abruptly, often reaching 39 to 40 degrees centigrade and accompanied by intermittent shaking chills. This acute phase lasts 2-3 days. The temperature may remit for 1-2 days, resulting in a "saddle-back" fever curve.
The arthralgias are polyarticular, migratory, and predominantly affect the small joints of the hands, wrists, ankles and feet, with lesser involvement of larger joints. Pain on movement is worse in the morning, improved by mild exercise, and exacerbated by strenous exercise. Swelling may occur, but fluid accumulation is uncommon. Patients with milder articular manifestations are usually symptom-free within a few weeks, but more severe cases require months to resolve entirely. Generalized myalgia, as well as back and shoulder pain, is common.
Cutaneous manifestations are typical with many patients presenting with a flush over the face and trunk. This is usually followed by a rash generally described as maculopapular. The trunks and limbs are commonly involved, but face, palms and soles may also show lesions. Pruritis or irritation may accompany the eruption.
During the acute disease, most patients will have headache, but it is not usually severe. Photophobia and retroorbital pain also occur but not severe. Conjunctival injection is present in some cases. Some patients will complain of sore throat and have pharyngitis on examination.
CHIK infection has a somewhat different picture in younger patients. Arthralgia and arthritis occur but are less prominent and last a shorter time. Rash may be less frequent; but in infants and younger children, prominent flushing and early appearance of maculopapular or urticarial eruption may be a useful indicator.
In Asia, several virus isolations have been made from severely ill children diagnosed as having haemorrhagic fever, similar to DHF.
Treatment
Supportive care with rest is indicated during the acute joint symptoms. Movement and mild exercise tend to improve stiffness and morning arthralgia, but heavy exercise may exacerbate rheumatic symptoms. In unresolved arthritis refractory to aspirin and nonsteroidal antiinflammatory drugs, chloroquine phosphate (250 mg/day) has given promising results.
Diagnosis
The definitive diagnosis can only be made by laboratory means, but CHIK should be suspected when epidemic disease occurs with the characteristic triad of fever, rash and rheumatic manifestations.
Virus isolation is readily accomplished by inoculation of mosquito cell culture, mosquito, mammalian cell culture or suckling mice. Viremia will be present in most patients during the first 48 hours of disease and may be detected as late as day 4 in some patients.
Virus-specific IgM antibodies are readily detected by capture ELISA in patients recovering from CHIK infection and they persist in excess of 6 months. Haemagglutination inhibition (HI) antibodies appear with the cessation of viremia. All patients will be positive by day 5 to 7 of illness. Neutralization antibodies parallel HI antibodies.
Chikungunya IgM serology test is available in University Malaya.
ALPHAVIRUSES
S.K. Lam and K.B. Chua, WHO Collaborating Centre for Arbovirus Reference and Research (DF/DHF), Department of Medical Microbiology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur.
SOURCE : FIELDS VIROLOGY (3<sup>RD</sup> EDITION)
Chikungunya virus
CHIK is responsible for extensive Aedes aegypti-transmitted urban disease in cities in Africa and major epidemics in Asia. The crippling arthralgia and frequent arthritis that accompany the fever and other systemic symptoms are clinically distinct. Several other togaviruses of the alphavirus genus (Ross River, O?nyong-nyong, etc) have been associated with a similar syndrome. CHIK activity in Asia has been documented since its isolation in Bangkok in 1958. Other countries which have reported CHIK activity include Cambodia, Vietnam, Myanmar, Sri Lanka, India, Indonesia, and the Philippines.
CHIK virus is transmitted in the savannahs and forests of tropical Africa by Aedes mosquitoes of the subgenera Stegomyia and Diceromyia. Aedes aegypti is an important vector in urban epidemics in both Africa and Asia.
Clinical Features
CHIK is an acute infection of abrupt onset, heralded by fever and severe arthralgia, followed by other constitutional symptoms and rash, and lasting for a period of 1-7 days. The incubation period is usually 2-3 days, with a range of 1-12 days. Fever rises abruptly, often reaching 39 to 40 degrees centigrade and accompanied by intermittent shaking chills. This acute phase lasts 2-3 days. The temperature may remit for 1-2 days, resulting in a "saddle-back" fever curve.
The arthralgias are polyarticular, migratory, and predominantly affect the small joints of the hands, wrists, ankles and feet, with lesser involvement of larger joints. Pain on movement is worse in the morning, improved by mild exercise, and exacerbated by strenous exercise. Swelling may occur, but fluid accumulation is uncommon. Patients with milder articular manifestations are usually symptom-free within a few weeks, but more severe cases require months to resolve entirely. Generalized myalgia, as well as back and shoulder pain, is common.
Cutaneous manifestations are typical with many patients presenting with a flush over the face and trunk. This is usually followed by a rash generally described as maculopapular. The trunks and limbs are commonly involved, but face, palms and soles may also show lesions. Pruritis or irritation may accompany the eruption.
During the acute disease, most patients will have headache, but it is not usually severe. Photophobia and retroorbital pain also occur but not severe. Conjunctival injection is present in some cases. Some patients will complain of sore throat and have pharyngitis on examination.
CHIK infection has a somewhat different picture in younger patients. Arthralgia and arthritis occur but are less prominent and last a shorter time. Rash may be less frequent; but in infants and younger children, prominent flushing and early appearance of maculopapular or urticarial eruption may be a useful indicator.
In Asia, several virus isolations have been made from severely ill children diagnosed as having haemorrhagic fever, similar to DHF.
Treatment
Supportive care with rest is indicated during the acute joint symptoms. Movement and mild exercise tend to improve stiffness and morning arthralgia, but heavy exercise may exacerbate rheumatic symptoms. In unresolved arthritis refractory to aspirin and nonsteroidal antiinflammatory drugs, chloroquine phosphate (250 mg/day) has given promising results.
Diagnosis
The definitive diagnosis can only be made by laboratory means, but CHIK should be suspected when epidemic disease occurs with the characteristic triad of fever, rash and rheumatic manifestations.
Virus isolation is readily accomplished by inoculation of mosquito cell culture, mosquito, mammalian cell culture or suckling mice. Viremia will be present in most patients during the first 48 hours of disease and may be detected as late as day 4 in some patients.
Virus-specific IgM antibodies are readily detected by capture ELISA in patients recovering from CHIK infection and they persist in excess of 6 months. Haemagglutination inhibition (HI) antibodies appear with the cessation of viremia. All patients will be positive by day 5 to 7 of illness. Neutralization antibodies parallel HI antibodies.
Chikungunya IgM serology test is available in University Malaya.
ALPHAVIRUSES
S.K. Lam and K.B. Chua, WHO Collaborating Centre for Arbovirus Reference and Research (DF/DHF), Department of Medical Microbiology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur.
SOURCE : FIELDS VIROLOGY (3<sup>RD</sup> EDITION)